1. Field of the Invention
One embodiment of the present invention relates to a power storage unit and a manufacturing method thereof.
Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. In addition, one embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter.
Note that in this specification, the power storage unit is a collective term describing units and devices having a power storage function. Examples of the power storage unit include a battery, a primary battery, a secondary battery, a lithium-ion secondary battery, a lithium-air secondary battery, a capacitor, and a lithium-ion capacitor. Also in this specification, the electrochemical device is a collective term describing devices that can function using a power storage unit, a conductive layer, a resistor, a capacitor, and the like. In addition, an electronic device, an electric appliance, a mechanical device, and the like each include a power storage unit according to one embodiment of the present invention in some cases.
In this specification and the like, a semiconductor device generally means a device that can function by utilizing semiconductor characteristics. A display device (e.g., a liquid crystal display device and a light-emitting display device), a lighting device, an electro-optical device, a power storage device, a memory device, a semiconductor circuit, an imaging device, an electronic device, and the like may include a semiconductor device.
2. Description of the Related Art
In recent years, a variety of power storage units, for example, secondary batteries such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries, have been actively developed. In particular, demand for lithium-ion secondary batteries with high output and high energy density has rapidly grown with the development of the semiconductor industry, for electronic devices, for example, portable information terminals such as cell phones, smartphones, and laptop computers, portable music players, and digital cameras; medical equipment; next-generation clean energy vehicles such as hybrid electric vehicles (HEVs), electric vehicles (EVs), and plug-in hybrid electric vehicles (PHEVs); and the like. The lithium-ion secondary batteries are essential as rechargeable energy supply sources for today's information society.
The performance required for the lithium-ion batteries includes increased energy density, improved cycle characteristics, safe operation under a variety of environments, and longer-term reliability.
Also in recent years, flexible display devices have been proposed to be mounted on a curved surface or worn on the human body such as head. This has increased demand for flexible power storage units that can be attached to a curved surface. For example, Patent Document 1 discloses a power storage unit whose flexibility is increased with a wave-shaped exterior body.